Printing – Stenciling – Traveling-inker machines
Reexamination Certificate
1999-12-28
2002-12-17
Funk, Stephen R. (Department: 2854)
Printing
Stenciling
Traveling-inker machines
Reexamination Certificate
active
06494132
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a screen printer and its screen printing method. Particularly, this invention relates to the screen printer using a plurality of squeegees. This invention also relates to the screen printer using a pressure unit for pressing a screen.
2. Description of the Related Art
FIG. 12
illustrates a perspective view of the screen printer.
FIG. 13
illustrates a schematic side view of the screen printer.
FIG. 14
illustrates a schematic top view of the screen printer.
In
FIG. 12
, a screen printer
101
, a base of the screen printer
102
, a table
103
which is attached for allowing movement, a guide rail
104
for guiding the movement of the table, an operation box
105
of the screen printer, an operation switch
107
attached to the operation box, and a printing unit
109
for performing screen printing on a work placed on the table
103
are illustrated. In
FIGS. 13 and 14
, a work
110
placed on the table
103
, a screen plate
200
, a screen frame
1
of the screen plate
200
, and a screen
201
affixed to the screen plate
200
are illustrated. A slider
106
for holding a squeegee
111
and a scraper (not illustrated) slides in directions of arrow A and arrow D, and a slide base
108
slides the slider
106
.
The table
103
is attached for allowing left and right sliding along the guide rail
104
provided on the base
102
. When the table
103
moves under the printing unit
109
, the table
103
is stopped by a stopper (not illustrated), and the printing unit
109
performs screen printing on the work
110
.
FIG. 15
illustrate an example of the screen plate
200
.
The screen plate
200
for a combination screen is illustrated in FIG.
15
.
In
FIG. 15
, the screen frame
1
, a support screen
2
, a print screen
3
, and a joint part
4
of the support screen and the print screen are illustrated. The screen
201
includes the support screen
2
, the print screen
3
, and the joint part
4
.
FIG. 16
illustrates a front surface of the print screen
3
.
FIG. 17
illustrates a back surface of the print screen
3
.
In
FIGS. 16 and 17
, a screen-mesh
30
, and an emulsion
31
provided on a back of the screen-mesh
30
are illustrated. An opening
32
is provided in the emulsion
31
. The opening
32
is provided for generating a print image. When an ink (paste) passes through the opening and sticks to the work
110
, screen printing is performed on the work.
FIGS. 18 and 19
show cross-sectional views at X—X part of the screen printer illustrated in
FIG. 14. A
squeegee holder
120
and a scraper holder
320
are attached to the slider
106
for allowing up and down movement by a mechanism which is not illustrated. In
FIG. 18
, the slider
106
is moving in the direction of arrow A, and the squeegee
111
, secured for example, against squeegee bracket
111
a
, is pushed down in the direction of arrow B. Printing is performed on the work
110
by using an ink
51
. The scraper holder
320
holds a scraper
311
, and the scraper holder is moved up in a direction of arrow C during a printing operation by the squeegee. When printing is performed by using the squeegee
111
, printing is performed with a high pressure. As illustrated in
FIG. 18
, the screen is pressed by a pressure applied to the squeegee at a point R in which the squeegee and the screen contact each other. When the squeegee moves, the point R moves on the surface of the screen.
In case of
FIG. 19
, the slider moves in a direction of arrow D. When the slider moves in the direction of arrow D, the squeegee holder
120
is pulled up in a direction of arrow E. At the same time, the scraper holder
320
is pushed down in a direction of arrow F, and the scraper
311
moves on the surface of the screen in contact with the screen
201
. The scraper
311
has a function for pushing the ink
51
, which has been moved to a right side of
FIG. 19
by the squeegee
111
, back to a left side of FIG.
19
. The scraper
311
also has a function for re-coating the surface of the screen evenly with the ink after printing is performed by the squeegee
111
.
The screen printer performs screen printing by moving the squeegee
111
in the direction of arrow A as illustrated in FIG.
18
. As illustrated in
FIG. 19
, when the slider is moved in the direction of arrow D, the ink is returned, and the surface of the screen is evenly re-coated with the ink.
FIG. 20
illustrates a sectional view of the screen in case that the squeegee
111
in
FIG. 18
has performed printing on the work
110
. The ink
51
passes through the opening
32
of the emulsion provided on the back side of the screen-mesh, and sticks to the work
110
. Since the squeegee
111
is made of an elastic material, e.g., urethane rubber, etc., when the squeegee
111
has passed, the ink
51
on the surface of the screen is evenly scraped.
In
FIG. 21
, the scraper
311
returns the ink. The scraper
311
is made of a metal, e.g., stainless, etc. The scraper includes a taper part
312
at an end, and contacts with the surface of the screen at point Q. Since the scraper
311
is made of the metal, e.g., stainless, etc., when the scraper
311
has passed, the surface of the screen is evenly coated with the ink
51
. In this way, an evenly coated condition is generated. Therefore, next printing can be performed evenly by the squeegee
111
.
FIG. 22
illustrates the printing unit
109
in a printing state. The screen
201
is evenly coated with the ink
51
.
(a) of
FIG. 22
illustrates a state before starting printing. In (b) of
FIG. 22
, a pressure P is applied to the squeegee
111
, and printing is started. In (c) of
FIG. 22
, patterns
52
,
53
and
54
have been printed on the work
110
from patterns which are generated on the screen
201
in advance. In (d) of
FIG. 22
illustrates a time of completing printing is illustrated further including patterns
55
and
56
. During printing in (b)-(d) of
FIG. 22
, the pressure P applied to the squeegee
111
is constant as shown in (e) of FIG.
22
.
When printing is performed as illustrated in
FIG. 22
, a height H
1
of the pattern
52
and a height H
2
of the pattern
54
illustrated in (d) of
FIG. 22
may differ. Even though the screen
201
is tightly stretched over the screen frame
1
, angles vary in positions on the screen
201
. Therefore, even if the constant pressure P is applied downward during printing, there is a possibility that a printed pattern may be spread forward in some printing position. Hence, such problems like uneven thickness of the ink on the work
110
and uneven printing have to be solved.
As shown in
FIG. 22
, angles &agr;, &bgr;, and &ggr; between the screen
201
and the work
110
change during printing (&agr;<&bgr;<&ggr;). Since the angles between the screen
201
and the work
110
vary in printing positions, there are solving problems such as uneven thickness of the ink on the work
110
and uneven printing.
FIG. 23
illustrates a method for solving the above-stated uneven thickness of the ink.
In
FIG. 23
, during printing, the screen plate
200
is lifted up in a direction of arrow X by using a detaching apparatus (plate detaching apparatus) which is not illustrated. By detaching the screen plate
200
from a side in which printing is finished, changes in a tension in the positions on the screen
201
are intended to be ignored. Consequently, the height H
1
of the pattern
52
and, for example, pattern
56
printed at an edge area of the work
110
and the height H
2
of the pattern
54
printed at a center of the work
110
can become almost equal with the height patters
53
and
55
also being almost equal to edge patterns
52
and
56
and center pattern
54
.
However, according to the method of lifting one side of the screen plate
200
as illustrated in
FIG. 23
, an excessive pressure is applied to the screen plate
200
. As a result, printing patterns provided on the screen
201
might be shifted, and a durability of the screen plate
200
might be reduced.
FIG. 24
illustrates a sc
Sano Yasushi
Tanaka Osamu
Funk Stephen R.
Micro-Tec Company Ltd.
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